The trackside closure devices for bottom and side discharge and railway hopper cars have gone through substantial development over the years. Several devices have used rotating closure members for engaging a fitting on the hopper door. Peterson, U.S. Pat. No. 3,891,101, discloses a trackside closure device which uses a rotating mechanism having three radially-spaced actuating arms to close bottom doors on moving hopper cars. The arms have ball-ends which are resiliently mounted to absorb shock, and the ball-ends engage a socket on the car door to force the door closed before the receiving socket opens to allow disengagement of the actuating arm. The arms must be carefully indexed to provide for proper positioning of the arm for accurate engagement of the socket on the next hopper door.
Green et al., U.S. Pat. No. 4,011,956, discloses a modification of the Peterson closure mechanism. The Green mechanism includes a single rotating actuating arm adapted to engage a socket in the doors of a hopper car as they move along a track adjacent to the closure mechanism. Again, the actuating arm has an engaging member located at its end. The engaging member is resiliently mounted (telescoping) in the actuating arm to allow for substantial compression of the actuating arm. After closing the hopper car door, the actuating arm is released from the socket, the arm maintains a compressed configuration, an electric motor returns the actuating arm in the compressed configuration toward an indexed position to wait for the next door, the actuating arm is extended to full length, and arrives at the indexing position. Because the actuating arm completes the closure process at a point removed from the indexing position, there is a time delay during which the arm resets. This time delay can limit the speed at which the train can move during the closure operation.
Both the Peterson and Green et al. references require careful control of the relative position of the end of the actuating arm and the socket on the hopper car door to ensure proper cooperation of the device in closing the door. Further, these devices are susceptible to deformation of the actuating arms which would impair the ability of the end to be accurately positioned with respect to the hopper car door and in the telescoping arrangement within the arm itself. In addition, the Green device requires an electric motor to return the actuating arm to the indexed position, and the recovery time required to reposition the arm may limit the train's speed during the operation. Therefore, more durable and simple closure mechanisms are required which have essentially no recovery time.
Miller et al., U.S. Pat. No. 4,120,412, discloses a trackside closing arrangement for railway hopper cars including a pair of pneumatic tires and wheels mounted on a pivot arm. The tires rotate in an essentially horizontal plane and are inter-connected and mounted concentrically on the pivot arm at trackside to contact and close hopper doors on railway cars. Unlike the Peterson and Green references, the closure devices of Miller et al. do not appear to be capable of projecting into or underneath a hopper car to close a door. Therefore, the hopper doors of Miller et al. project outward from the car to contact the closure device. In addition, a pair of closure mechanisms positioned on opposite sides of a railroad tack are linked to provide coordinated movement and maintain contact with a swaying hopper car.
Railway hopper cars are often utilized in unit train operations. Such trains consist entirely of hoppers carrying coal or other comminuted materials which are dumped downwardly through the tracks into a suitable bin arrangement when the train arrives at its destination. A recent development in such unit trains is disclosed in Kieres, U.S. Pat. No. 4,754,710. Kieres discloses a segmented railway car which can be 500 feet long. The end of each segment is supported by wheel-containing truck means. The railroad car of Kieres includes a plurality of side discharge openings closed by swinging doors. These doors close on sills and can be wholly within the region defined by the vertical side walls of the car. In order to close these doors, it may be necessary that a closure device extend into or underneath a hopper car.
Trackside hopper car door closing mechanisms have addressed the interaction between the mechanism and car door in several ways. One way has been the "ball and socket" arrangement of Peterson and Green. This arrangement requires controlled relative positioning between the mechanism and a socket on the car door. In addition, the socket must be capable of releasing the ball end of the actuator arm flawlessly. The "ball and socket" type of closure mechanism is susceptible to damage and misalignment. Further, Green requires an electric motor to return the actuating arm to an indexed position. In an attempt to avoid the problems inherent in the "ball and socket" arrangement, Miller utilizes a pair of rotating pneumatic tires which contact modified hopper car doors. However, this arrangement requires that the hopper car doors be moved to project beyond the car body. This is necessary as the Miller device does not appear capable of projecting into or under a hopper car.
Therefore, a new trackside door closure device is needed which (1) is versatile and can operate with hopper car doors which project beyond a car body or which can itself project into or under a hopper car, (2) is durable and resilient resisting permanent deformation and misalignment, (3) which returns to an indexed or ready position before a newly closed hopper door moves from vicinity of the mechanism to be ready for the next open door and (4) which does not require electrical energization means.